Multilayer ceramic capacitor

ABSTRACT

A multilayer ceramic capacitor includes a multilayer body in which dielectric layers are layered, first internal electrode layers extending to opposing end surfaces of the multilayer body, second internal electrode layers extending to opposing side surfaces of the multilayer body, first and second external electrodes connected to the first internal electrode layers and provided on the respective opposing end surfaces, and third and fourth external electrodes connected to the second internal electrode layers and provided on the respective opposing side surfaces. A number of the first internal electrode layers is larger than a number of the second internal electrode layers, at least two first internal electrode layers are successively layered, and a thickness of the second internal electrode layers is larger than a thickness of the first internal electrode layers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2020-145003 filed on Aug. 28, 2020. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a multilayer ceramic capacitor.

2. Description of the Related Art

A multilayer through-type capacitor with a structure as described in Japanese Patent Laid-Open No. 2000-58376 has been known, for example, as an anti-noise component of a decoupling capacitor used for stabilizing a power supply voltage supplied to an integrated circuit (IC) component that operates at a high speed or a line for power supply to an integrated circuit (IC) component. The through-type capacitor described in Japanese Patent Laid-Open No. 2000-58376 includes a ceramic element (multilayer body) including an outer surface including first and second main surfaces opposed to each other, first and second side surfaces opposed to each other, and first and second end surfaces opposed to each other. In the inside of the ceramic element, a plurality of first internal electrodes and a plurality of second internal electrodes are alternately arranged in a direction of layering. The first internal electrode includes opposing ends extending to the first and second end surfaces, and the second internal electrode includes opposing ends extending to the first and second side surfaces.

In such a multilayer through-type capacitor, to lower a capacitance, the number of internal electrodes should be reduced and thus a value of a direct-current (DC) resistance (Rdc) of the internal electrode becomes large. Accordingly, an amount of heat generation in the multilayer through-type capacitor may be large.

As in Japanese Patent Laid-Open No. 9-55335, a structure in which a plurality of through electrodes are successively layered has been known as a structure that can achieve suppression of an increase in DC resistance an while increase in capacitance is suppressed. Since a value of the DC resistance (Rdc) can also be made smaller while the capacitance is lowered according to the structure described in Japanese Patent Laid-Open No. 9-55335, the amount of heat generation can also be suppressed.

In an attempt to further lower a capacitance in the structure as described in Japanese Patent Laid-Open No. 9-55335, however, ground electrodes extending to opposing side surfaces of the multilayer body should be reduced. In that case, since connection portions between the ground electrodes and the external electrodes are reduced, connectivity therebetween may not be sufficiently provided.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide multilayer ceramic capacitors that are each able to achieve reduction or prevention of an increase in DC resistance while achieving a lower capacitance thereof and each are further able to ensure connectivity between an internal electrode layer and an external electrode.

A multilayer ceramic capacitor according to a preferred embodiment of the present invention includes a multilayer body including a plurality of layered dielectric layers, the multilayer body including a first main surface and a second main surface opposed to each other in a height direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the height direction, and a first side surface and a second side surface opposed to each other in a width direction orthogonal or substantially orthogonal to the height direction and the length direction, a plurality of first internal electrode layers on the plurality of dielectric layers and extending to the first end surface and the second end surface, a plurality of second internal electrode layers on the plurality of dielectric layers and extending to the first side surface and the second side surface, a first external electrode on the first end surface and connected to the first internal electrode layers, a second external electrode on the second end surface and connected to the first internal electrode layers, a third external electrode on the first side surface and connected to the second internal electrode layers, and a fourth external electrode on the second side surface and connected to the second internal electrode layers. A number of the first internal electrode layers is larger than a number of the second internal electrode layers, at least two of the first internal electrode layers are successively layered, and each of the second internal electrode layers has a thickness larger than a thickness of each of the first internal electrode layers.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to a preferred embodiment of the present invention.

FIG. 2 is a top view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to a preferred embodiment of the present invention.

FIG. 3 is a side view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to a preferred embodiment of the present invention.

FIG. 4 is a cross-sectional view along the line IV-IV in FIG. 1 .

FIG. 5 is a cross-sectional view along the line V-V in FIG. 1 .

FIG. 6 is a cross-sectional view along the line VI-VI in FIG. 4 .

FIG. 7 is a cross-sectional view along the line VII-VII in FIG. 4 .

FIG. 8 shows a modification of a second internal electrode layer shown in FIG. 7 .

FIG. 9 is a cross-sectional view showing an exemplary multilayer ceramic capacitor (Comparative Example 1-3) according to Comparative Example 1.

FIG. 10 is a cross-sectional view showing an exemplary multilayer ceramic capacitor (Comparative Example 2-3) according to Comparative Example 2.

FIG. 11 is a diagram showing heat generation characteristics with variations in value of a current between external electrodes in multilayer ceramic capacitors in Example of a preferred embodiment of the present invention, Comparative Example 1, and Comparative Example 2.

FIG. 12 is a diagram showing a value of a DC resistance depending on a difference in capacitance in multilayer ceramic capacitors in Example and Comparative Example 1.

FIG. 13 is a diagram showing a relationship between the number of layered second internal electrodes and a ratio of defective connection in multilayer ceramic capacitors in Example and Comparative Example 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described below with reference to the drawings.

1. Multilayer Ceramic Capacitor

A multilayer ceramic capacitor according to a preferred embodiment of the present invention will be described. The multilayer ceramic capacitor according to the present preferred embodiment is a three-terminal multilayer ceramic capacitor, for example.

FIG. 1 is an external perspective view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to a preferred embodiment of the present invention. FIG. 2 is a top view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to the present preferred embodiment of the present invention. FIG. 3 is a side view showing an exemplary multilayer ceramic capacitor (three-terminal multilayer ceramic capacitor) according to the present preferred embodiment of the present invention. FIG. 4 is a cross-sectional view along the line IV-IV in FIG. 1 . FIG. 5 is a cross-sectional view along the line V-V in FIG. 1 . FIG. 6 is a cross-sectional view along the line VI-VI in FIG. 4 . FIG. 7 is a cross-sectional view along the line VII-VII in FIG. 4 . FIG. 8 shows a modification of a second internal electrode layer shown in FIG. 7 .

As shown in FIGS. 1 to 3 , a multilayer ceramic capacitor 10 includes a multilayer body 12 in a shape, for example, of a parallelepiped and an external electrode 30.

Multilayer body 12 includes a plurality of layered dielectric layers 14 and a plurality of internal electrode layers 16 on dielectric layer 14. Multilayer body 12 includes a first main surface 12 a and a second main surface 12 b opposed to each other in a height direction x, a first side surface 12 c and a second side surface 12 d opposed to each other in a width direction y orthogonal or substantially orthogonal to height direction x, and a first end surface 12 e and a second end surface 12 f opposed to each other in a length direction z orthogonal or substantially orthogonal to height direction x and width direction y. Multilayer body 12 includes a rounded corner and a rounded ridgeline. The corner refers to a portion where three adjacent surfaces of the multilayer body meet one another and the ridgeline refers to a portion where two adjacent surfaces of the multilayer body meet each other. Projections and recesses or the like may be provided in a portion or an entirety of first main surface 12 a and second main surface 12 b, first side surface 12 c and second side surface 12 d, and first end surface 12 e and second end surface 12 f.

A dimension of multilayer body 12 is not particularly limited.

Multilayer body 12 includes an inner layer portion 18 and a first main-surface-side outer layer portion 20 a and a second main-surface-side outer layer portion 20 b arranged to sandwich inner layer portion 18 in height direction x.

Inner layer portion 18 includes a plurality of dielectric layers 14 and a plurality of internal electrode layers 16. Inner layer portion 18 includes internal electrode layers from internal electrode layer 16 located closest to first main surface 12 a in height direction x to internal electrode layer 16 located closest to second main surface 12 b. In inner layer portion 18, the plurality of internal electrode layers 16 opposed to each other with dielectric layer 14 interposed therebetween. Inner layer portion 18 produces a capacitance and defines and functions as a capacitor.

First main-surface-side outer layer portion 20 a is located on a side of first main surface 12 a. First main-surface-side outer layer portion 20 a includes a plurality of dielectric layers 14 located between first main surface 12 a and internal electrode layer 16 closest to first main surface 12 a.

Second main-surface-side outer layer portion 20 b is located on a side of second main surface 12 b. Second main-surface-side outer layer portion 20 b includes a plurality of dielectric layers 14 located between second main surface 12 b and internal electrode layer 16 closest to second main surface 12 b.

Dielectric layers 14 included in each of first main-surface-side outer layer portion 20 a and second main-surface-side outer layer portion 20 b may be the same or substantially the same as dielectric layers 14 included in inner layer portion 18.

Multilayer body 12 includes a first side-surface-side outer layer portion 22 a located on a side of first side surface 12 c and including a plurality of dielectric layers 14 located between first side surface 12 c and an outermost surface of inner layer portion 18 on the side of first side surface 12 c.

Similarly, multilayer body 12 includes a second side-surface-side outer layer portion 22 b located on a side of second side surface 12 d and including a plurality of dielectric layers 14 located between second side surface 12 d and an outermost surface of inner layer portion 18 on the side of second side surface 12 d.

FIG. 5 shows a range in width direction y of each of first side-surface-side outer layer portion 22 a and second side-surface-side outer layer portion 22 b. A magnitude of a width in width direction y of each of first side-surface-side outer layer portion 22 a and second side-surface-side outer layer portion 22 b is also referred to as a W gap or a side gap.

Multilayer body 12 includes a first end-surface-side outer layer portion 24 a located on a side of first end surface 12 e and including a plurality of dielectric layers 14 located between first end surface 12 e and an outermost surface of inner layer portion 18 on the side of first end surface 12 e.

Similarly, multilayer body 12 includes a second end-surface-side outer layer portion 24 b located on a side of second end surface 12 f and including a plurality of dielectric layers 14 located between second end surface 12 f and an outermost surface of inner layer portion 18 on the side of second end surface 12 f.

FIG. 4 shows a range in length direction z of each of first end-surface-side outer layer portion 24 a and second end-surface-side outer layer portion 24 b. A magnitude of a width in length direction z of each of first end-surface-side outer layer portion 24 a and second end-surface-side outer layer portion 24 b is also referred to as an L gap or an end gap.

Dielectric layer 14 can be made of, for example, a dielectric material as a ceramic material. For example, dielectric ceramics including a component such as BaTiO₃, CaTiO₃, SrTiO₃, or CaZrO₃ can be used as a dielectric material. When the dielectric material is included as a main component, depending on a characteristic of desired multilayer body 12, for example, a sub-component lower in content than the main component, such as an Mn compound, an Fe compound, a Cr compound, a Co compound, or an Ni compound may be added.

Fired dielectric layer 14 preferably has a thickness not smaller than about 0.5 μm and not larger than about 10 μm, for example.

The number of layered dielectric layers 14 is preferably not smaller than fifteen and not larger than three hundred, for example. The number of dielectric layers 14 is a total of the number of dielectric layers 14 in inner layer portion 18 and the number of dielectric layers 14 in first main-surface-side outer layer portion 20 a and second main-surface-side outer layer portion 20 b.

Multilayer body 12 includes a plurality of first internal electrode layers 16 a and a plurality of second internal electrode layers 16 b as the plurality of internal electrode layers 16.

First internal electrode layer 16 a is on dielectric layer 14.

As shown in FIG. 6 , first internal electrode layer 16 a includes a first section 26 a that extends between first end surface 12 e and second end surface 12 f of multilayer body 12 and corresponds to a central portion thereof, a second section 26 b that extends from first section 26 a and extends to first end surface 12 e of multilayer body 12 e, and a third section 26 c that extends from first section 26 a to second end surface 12 f of multilayer body 12. First section 26 a is located in the central portion on dielectric layer 14. Second section 26 b is exposed at first end surface 12 e of multilayer body 12 and third section 26 c is exposed at second end surface 12 f of multilayer body 12. Therefore, first internal electrode layer 16 a is not exposed at first side surface 12 c and second side surface 12 d of multilayer body 12.

Although a shape of first internal electrode layer 16 a is not particularly limited, first internal electrode layer 16 a is preferably rectangular or substantially rectangular and includes a rounded corner, for example.

Second internal electrode layer 16 b is provided on dielectric layer 14 different from dielectric layer 14 on which first internal electrode layer 16 a is provided.

As shown in FIG. 7 , second internal electrode layer 16 b includes a fourth section 28 a that extends between first side surface 12 c and second side surface 12 d of multilayer body 12 and corresponds to a central portion thereof, a fifth section 28 b that extends from fourth section 28 a to first side surface 12 c, and a sixth section 28 c that extends from fourth section 28 a to second side surface 12 d. Fourth section 28 a has a rectangular or substantially rectangular shape extending toward first end surface 12 e and extending toward second end surface 12 f. Fourth section 28 a is located in the central portion on dielectric layer 14. Fifth section 28 b is exposed at first side surface 12 c of multilayer body 12 and sixth section 28 c is exposed at second side surface 12 d of multilayer body 12. Therefore, second internal electrode layer 16 b is not exposed at first end surface 12 e and second end surface 12 f of multilayer body 12.

Although a shape of fourth section 28 a and a shape of each of fifth section 28 b and sixth section 28 c of second internal electrode layer 16 b are not particularly limited, the sections are preferably rectangular or substantially rectangular, for example. The corner of each section may be rounded.

First section 26 a of first internal electrode layer 16 a is opposed to fourth section 28 a of second internal electrode layer 16 b.

A width of first section 26 a of first internal electrode layer 16 a in width direction y that connects between first side surface 12 c and second side surface 12 d may be equal to or different from a width of fourth section 28 a of second internal electrode layer 16 b in width direction y that connects between first side surface 12 c and second side surface 12 d.

A relationship of A≥B is preferably satisfied, where A represents a width of fourth section 28 a of second internal electrode layer 16 b in length direction z that connects between first end surface 12 e and second end surface 12 f and B represents a width of fifth section 28 b and sixth section 28 c of second internal electrode layer 16 b in length direction z that connects between first end surface 12 e and second end surface 12 f.

For example, as shown in FIG. 8 , in a modification of second internal electrode layer 16 b, fourth section 28 a of second internal electrode layer 16 b may not extend toward first end surface 12 e and second end surface 12 f and width A of fourth section 28 a of second internal electrode layer 16 b in length direction z that connects between first end surface 12 e and second end surface 12 f may be equal or substantially equal to width B of each of fifth section 28 b and sixth section 28 c of second internal electrode layer 16 b in length direction z that connects between first end surface 12 e and second end surface 12 f.

Thus, by adjusting only an area of second internal electrode layer 16 b without changing an area of first internal electrode layer 16 a, a capacitance of multilayer ceramic capacitor 10 can be lowered with a DC resistance remaining low.

Although not shown, a relationship of A<B may be satisfied.

First internal electrode layers 16 a are larger in number than second internal electrode layers 16 b, and at least two first internal electrode layers 16 a are successively layered. Thus, multilayer ceramic capacitor 10 shown in FIG. 1 is not only larger in number of first internal electrode layers 16 a and larger in number of first internal electrode layers 16 a connected in parallel while an increase in capacitance is reduced or prevented, but is also improved in conduction between first internal electrode layers 16 a and external electrode 30, and thus achieves reduction or prevention of an increase in DC resistance. Second internal electrode layer 16 b is larger in thickness than first internal electrode layer 16 a. Thus, even when the capacitance is lowered, connectivity between second internal electrode layers 16 b and external electrode 30 can also sufficiently be ensured.

Although the number of first internal electrode layers 16 a is not particularly limited, for example, it is preferably not smaller than thirty and not larger than one hundred, for example.

The number of second internal electrode layers 16 b is at least smaller than the number of first internal electrode layers 16 a. Specifically, although the number of second internal electrode layers 16 b is not particularly limited, for example, it is preferably not smaller than one and not larger than fifty.

Although a thickness of first internal electrode layer 16 a is not particularly limited, for example, the thickness is preferably not smaller than about 0.5 μm and not larger than about 2.0 μm.

Second internal electrode layer 16 b is at least larger in thickness than first internal electrode layer 16 a. Specifically, although the thickness of second internal electrode layer 16 b is not particularly limited, for example, the thickness is preferably not smaller than about 1 μm and not larger than about 3 μm.

The thickness of first internal electrode layer 16 a and the thickness of second internal electrode layer 16 b preferably satisfy a relationship of the thickness of the second internal electrode layer/the thickness of the first internal electrode layer≥about 1.2. Thus, even when a smaller number of second internal electrode layers 16 b are layered, connectivity between second internal electrode layers 16 b and external electrode 30 can be further improved.

Inner layer portion 18 of multilayer body 12 includes a capacitance forming portion 19 in which first internal electrode layer 16 a and second internal electrode layer 16 b are opposed to each other with dielectric layer 14 being interposed therebetween to produce a capacitance and an internal electrode layered portion 25 which is a region where at least two first internal electrode layers 16 a are successively layered. Multilayer ceramic capacitor 10 exhibits characteristics of the capacitor due to capacitance forming portion 19.

Internal electrode layered portion 25 is divided into a plurality of internal electrode layered portions by second internal electrode layers 16 b. Since an assembly of first internal electrode layers 16 a is thus distributed, a heat radiation effect can be improved and a temperature increase suppression effect can be achieved.

In multilayer ceramic capacitor 10 shown in FIG. 1 , internal electrode layered portion 25 is divided by two second internal electrode layers 16 b into a first internal electrode layered portion 25 a, a second internal electrode layered portion 25 b, and a third internal electrode layered portion 25 c as shown in FIG. 4 .

A single second internal electrode layer 16 b may be provided to divide internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a are successively layered. A larger number of first internal electrode layers 16 a can thus be layered and a DC resistance lowering effect can be achieved.

At least two second internal electrode layers 16 b may be successively layered to divide internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a are successively layered. Thus, even when the number of second internal electrode layers 16 b is smaller, connectivity between second internal electrode layers 16 b and external electrode 30 can be improved.

Second internal electrode layer 16 b may be provided in internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a located on the side of first main surface 12 a of multilayer body 12 are successively layered, that is, between first internal electrode layered portion 25 a and first main surface 12 a, and in internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a located on the side of second main surface 12 b of multilayer body 12 are successively layered, that is, between third internal electrode layered portion 25 c and second main surface 12 b. Since capacitance forming portion 19 can thus also be provided around first main-surface-side outer layer portion 20 a and second main-surface-side outer layer portion 20 b, some of the capacitance is obtained, a current path to a mount substrate can be short, and a low ESL effect can be obtained.

Second internal electrode layer 16 b does not have to be provided in internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a located on the side of first main surface 12 a of multilayer body 12 are successively layered, that is, between first internal electrode layered portion 25 a and first main surface 12 a, and in internal electrode layered portion 25 which is the region where at least two first internal electrode layers 16 a located on the side of second main surface 12 b of multilayer body 12 are successively layered, that is, between third internal electrode layered portion 25 c and second main surface 12 b. A distance from the surface of multilayer body 12 to capacitance forming portion 19 where the capacitance is produced is thus longer. Therefore, even when a crack runs from the surface of multilayer body 12 due to external load, an effect of lower a tendency toward deterioration of insulation resistance can be obtained.

Dielectric layer 14 adjacent to second internal electrode layer 16 b is preferably larger in thickness than dielectric layer 14 between first internal electrode layers 16 a. A larger number of first internal electrode layers 16 a can thus be layered, and the DC resistance lowering effect can be further increased.

First internal electrode layer 16 a and second internal electrode layer 16 b can be made of an appropriate conductive material including a metal such as, for example, Ni, Cu, Ag, Pd, or Au and an alloy including at least one of those metals, such as an Ag—Pd alloy.

External electrode 30 is provided on the side of each of first end surface 12 e and second end surface 12 f as well as on the side of each of first side surface 12 c and second side surface 12 d of multilayer body 12. External electrode 30 includes a first external electrode 30 a, a second external electrode 30 b, a third external electrode 30 c, and a fourth external electrode 30 d.

First external electrode 30 a is provided on first end surface 12 e of multilayer body 12. First external electrode 30 a extends from first end surface 12 e of multilayer body 12 to cover a portion of each of first main surface 12 a, second main surface 12 b, first side surface 12 c, and second side surface 12 d. First external electrode 30 a is electrically connected to second section 26 b of first internal electrode layer 16 a exposed at first end surface 12 e of multilayer body 12. First external electrode 30 a may be provided only on first end surface 12 e of multilayer body 12.

Second external electrode 30 b is provided on second end surface 12 f of multilayer body 12. Second external electrode 30 b extends from second end surface 12 f of multilayer body 12 to cover a portion of each of first main surface 12 a, second main surface 12 b, first side surface 12 c, and second side surface 12 d. Second external electrode 30 b is electrically connected to third section 26 c of first internal electrode layer 16 a exposed at second end surface 12 f of multilayer body 12. Second external electrode 30 b may be provided only on second end surface 12 f of multilayer body 12.

Third external electrode 30 c is provided on first side surface 12 c of multilayer body 12. Third external electrode 30 c extends from first side surface 12 c to cover a portion of each of first main surface 12 a and second main surface 12 b. Third external electrode 30 c is electrically connected to fifth section 28 b of second internal electrode layer 16 b exposed at first side surface 12 c of multilayer body 12. Third external electrode 30 c may be provided only on first side surface 12 c of multilayer body 12.

Fourth external electrode 30 d is provided on second side surface 12 d of multilayer body 12. Fourth external electrode 30 d extends from second side surface 12 d to cover a portion of each of first main surface 12 a and second main surface 12 b. Fourth external electrode 30 d is electrically connected to sixth section 28 c of second internal electrode layer 16 b exposed at second side surface 12 d of multilayer body 12. Fourth external electrode 30 d may be provided only on second side surface 12 d of multilayer body 12.

Since second internal electrode layer 16 b is larger in thickness than first internal electrode layer 16 a, connectivity between fifth section 28 b of second internal electrode layer 16 b and third external electrode 30 c arranged on first side surface 12 c can be ensured and connectivity between sixth section 28 c of second internal electrode layer 16 b and fourth external electrode 30 d arranged on second side surface 12 d can be ensured.

As long as the thickness of first internal electrode layer 16 a and the thickness of second internal electrode layer 16 b satisfy a relationship of the thickness of the second internal electrode layer/the thickness of the first internal electrode layer≥about 1.2, connectivity between fifth section 28 b of second internal electrode layer 16 b and third external electrode 30 c arranged on first side surface 12 c can be secured and connectivity between sixth section 28 c of second internal electrode layer 16 b and fourth external electrode 30 d arranged on second side surface 12 d can be ensured even when the number of second internal electrode layers 16 b is smaller.

External electrode 30 includes an underlying electrode layer 32 on the surface of multilayer body 12 and a plated layer 34 covering underlying electrode layer 32.

Underlying electrode layer 32 includes a first underlying electrode layer 32 a, a second underlying electrode layer 32 b, a third underlying electrode layer 32 c, and a fourth underlying electrode layer 32 d.

First underlying electrode layer 32 a is on the surface of first end surface 12 e of multilayer body 12 and extends from first end surface 12 e to cover a portion of each of first main surface 12 a, second main surface 12 b, first side surface 12 c, and second side surface 12 d.

Second underlying electrode layer 32 b is on the surface of second end surface 12 f of multilayer body 12 and extends from second end surface 12 f to cover a portion of each of first main surface 12 a, second main surface 12 b, first side surface 12 c, and second side surface 12 d.

First underlying electrode layer 32 a may be provided only on the surface of first end surface 12 e of multilayer body 12 and second underlying electrode layer 32 b may be provided only on the surface of second end surface 12 f of multilayer body 12.

Third underlying electrode layer 32 c is on the surface of first side surface 12 c of multilayer body 12 and extends from first side surface 12 c to cover a portion of each of first main surface 12 a and second main surface 12 b.

Fourth underlying electrode layer 32 d is on the surface of second side surface 12 d of multilayer body 12 and extends from second side surface 12 d to cover a portion of each of first main surface 12 a and second main surface 12 b.

Third underlying electrode layer 32 c may be provided only on the surface of first side surface 12 c of multilayer body 12 and fourth underlying electrode layer 32 d may be provided only on the surface of second side surface 12 d of multilayer body 12.

Underlying electrode layer 32 includes, for example, at least one selected from a baked layer, a conductive resin layer, a thin layer, and the like.

A construction in which underlying electrode layer 32 is a baked layer, a conductive resin layer, or a thin layer will be described below.

Baked Layer

The baked layer includes a glass component and a metal component. The glass component for the baked layer includes, for example, at least one selected from B, Si, Ba, Mg, Al, Li, and the like, for example. The metal component for the baked layer includes at least one selected, for example, from Cu, Ni, Ag, Pd, an Ag—Pd alloy, Au, and the like, for example. The baked layer may include a plurality of layers. The baked layer is obtained by applying a conductive paste including a glass component and a metal component to multilayer body 12 and baking the conductive paste. The baked layer may be obtained by simultaneously firing a multilayer chip including internal electrode layers 16 and dielectric layers 14 and the conductive paste applied to the multilayer chip, or may be obtained by firing a multilayer chip including internal electrode layers 16 and dielectric layers 14 to obtain multilayer body 12 and thereafter applying a conductive paste to multilayer body 12 and baking multilayer body 12. When the baked layer is obtained by simultaneously firing the multilayer chip including internal electrode layers 16 and dielectric layers 14 and the conductive paste applied to the multilayer chip, the baked layer is preferably formed by baking a material to which a dielectric material is added, instead of the glass component.

A thickness in the direction of connection between first end surface 12 e and second end surface 12 f, of first underlying electrode layer 32 a located on first end surface 12 e at the central portion in height direction x is preferably not smaller than about 3 μm and not larger than about 70 μm, for example.

A thickness in the direction of connection between first end surface 12 e and second end surface 12 f, of second underlying electrode layer 32 b located on second end surface 12 f at the central portion in height direction x is preferably not smaller than about 3 μm and not larger than about 70 μm, for example.

When underlying electrode layer 32 is provided on a portion of first main surface 12 a and a portion of second main surface 12 b as well as on a portion of first side surface 12 c and a portion of second side surface 12 d, a thickness of first underlying electrode layer 32 a located on first main surface 12 a and second main surface 12 b and on first side surface 12 c and second side surface 12 d in the height direction of connection between first main surface 12 a and second main surface 12 b at a central portion in length direction z is preferably, for example, not smaller than about 3 μm and not larger than about 40 μm, for example.

When underlying electrode layer 32 is provided on a portion of first main surface 12 a and a portion of second main surface 12 b as well as on a portion of first side surface 12 c and a portion of second side surface 12 d, a thickness of second underlying electrode layer 32 b located on first main surface 12 a and second main surface 12 b and on first side surface 12 c and second side surface 12 d in the height direction of connection between first main surface 12 a and second main surface 12 b at a central portion in length direction z is preferably, for example, not smaller than about 3 μm and not larger than about 40 μm, for example.

Conductive Resin Layer

The conductive resin layer may include a plurality of layers.

The conductive resin layer may be provided on the baked layer to cover the same, or may be directly provided on multilayer body 12.

The conductive resin layer includes a thermosetting resin and a metal, for example.

The conductive resin layer may completely cover underlying electrode layer 32 or may cover a portion of underlying electrode layer 32.

Since the conductive resin layer includes a thermosetting resin, it is more flexible than a conductive layer formed, for example, from a plated film or a fired product of a conductive paste. Therefore, even though a physical shock or a shock originating from a thermal cycle is applied to multilayer ceramic capacitor 10, the conductive resin layer defines and functions as a buffer layer and can prevent a crack in multilayer ceramic capacitor 10.

Ag, Cu, Ni, Sn, Bi, or an alloy thereof, for example, can be used as a metal to be included in the conductive resin layer.

Alternatively, metal powders including a surface coated with Ag, for example, can also be used. When using metal powders including a surface coated with, for example, Ag, Cu, Ni, Sn, Bi, or powders of an alloy thereof is/are preferably used for the metal powders. Conductive metal powders of Ag are preferably used as a conductive metal because Ag is suitable as an electrode material because of its specific resistance lowest among metals and Ag which is a precious metal is not oxidized and highly weather resistant and because a metal as a base material can be inexpensive while the characteristics of Ag are maintained.

Cu or Ni subjected to antioxidation treatment can also be used as a metal to be included in the conductive resin layer.

Metal powders including a surface coated with Sn, Ni, or Cu can also be used as a metal to be included in the conductive resin layer. When using metal powders including a surface coated with Sn, Ni, or Cu, Ag, Cu, Ni, Sn, or Bi or powders of an alloy thereof is/are preferably used for the metal powders.

The conductive resin layer preferably includes at least about 35 vol % and at most about 75 vol % of metal with respect to a volume of the conductive resin as a whole.

An average particle size of the metal included in the conductive resin layer is not particularly limited. A conductive filler may have an average particle size of, for example, not smaller than about 0.3 μm and not larger than about 10 μm.

The metal included in the conductive resin layer mainly provides current conduction in the conductive resin layer. Specifically, a current conduction path is provided in the conductive resin layer as a result of contact between the conductive fillers.

Although the metal included in the conductive resin layer may be spherical or may have a flat profile, spherical metal powders and metal powders having a flat profile are preferably used as being mixed.

Various known thermosetting resins such as, for example, an epoxy resin, a phenol resin, a urethane resin, a silicone resin, and a polyimide resin can be used as the resin in the conductive resin layer. Among these, the epoxy resin having excellent heat resistance, moisture resistance, and adhesiveness is one of a preferred resin.

The conductive resin layer preferably includes at least about 25 vol % and at most about 65 vol % of resin with respect to the volume of the conductive resin as a whole.

The conductive resin layer preferably includes a hardening agent together with the thermosetting resin. When the epoxy resin is used as a base resin, various known compounds such as, for example, a phenol-based compound, an amine-based compound, an acid anhydride-based compound, an imidazole-based compound, an active-ester-based compound, and an amide-imide-based compound can be used as the hardening agent for the epoxy resin.

The conductive resin layer located in the central portion in height direction x of multilayer body 12 located on each of first end surface 12 e and second end surface 12 f preferably has a thickness of, for example, not smaller than about 10 μm and not larger than about 150 μm.

Thin Layer

When a thin layer is provided as underlying electrode layer 32, the thin layer is a layer having a thickness of not larger than about 1 μm that is formed as deposition of metal particles by a thin film formation method such as sputtering or vapor deposition, for example.

Plated layer 34 includes a first plated layer 34 a, a second plated layer 34 b, a third plated layer 34 c, and a fourth plated layer 34 d.

First plated layer 34 a, second plated layer 34 b, third plated layer 34 c, and fourth plated layer 34 d include at least one selected, for example, from Cu, Ni, Sn, Ag, Pd, an Ag—Pd alloy, Au, and the like.

First plated layer 34 a covers first underlying electrode layer 32 a.

Second plated layer 34 b covers second underlying electrode layer 32 b.

Third plated layer 34 c covers third underlying electrode layer 32 c.

Fourth plated layer 34 d covers fourth underlying electrode layer 32 d.

Plated layer 34 may include a plurality of layers. In this case, plated layer 34 preferably has a two-layered structure of a lower plated layer of Ni plating provided on underlying electrode layer 32 and an upper plated layer of Sn plating provided on the lower plated layer.

Specifically, first plated layer 34 a includes a first lower plated layer and a first upper plated layer located on a surface of the first lower plated layer.

Second plated layer 34 b includes a second lower plated layer and a second upper plated layer located on a surface of the second lower plated layer.

Third plated layer 34 c includes a third lower plated layer and a third upper plated layer located on a surface of the third lower plated layer.

Fourth plated layer 34 d includes a fourth lower plated layer and a fourth upper plated layer located on a surface of the fourth lower plated layer.

The lower plated layer of Ni plating is used to prevent corrosion of underlying electrode layer 32 by solder used for mount of multilayer ceramic capacitor 10 and the upper plated layer of Sn plating is used to improve wettability of solder used for mount of multilayer ceramic capacitor 10 to facilitate mount.

One plated layer preferably has a thickness not smaller than about 2.0 μm and not larger than about 15.0 μm, for example.

External electrode 30 may include only a plated layer without providing underlying electrode layer 32.

A structure where a plated layer is provided without underlying electrode layer 32 will be described below, although it is not shown.

Any one or each of first external electrode 30 a to fourth external electrode 30 d may include no underlying electrode layer 32, and may include the plated layer directly provided on the surface of multilayer body 12. In other words, multilayer ceramic capacitor 10 may include a plated layer electrically connected to first internal electrode layer 16 a and second internal electrode layer 16 b. In such a case, the plated layer may be formed after a catalyst is disposed on the surface of multilayer body 12 as pre-treatment.

When the plated layer is provided directly on multilayer body 12 without providing underlying electrode layer 32, a reduction in thickness by magnitude of the thickness of underlying electrode layer 32 can be translated into a lower profile, that is, a decrease in thickness, or into a thickness of multilayer body 12, that is, a thickness of inner layer portion 18. Therefore, a degree of freedom in design of a thin chip can be improved.

The plated layer preferably includes a lower plated electrode on the surface of multilayer body 12 and an upper plated electrode on a surface of the lower plated electrode. Each of the lower plated electrode and the upper plated electrode preferably includes at least one metal selected, for example, from Cu, Ni, Sn, Pb, Au, Ag, Pd, Bi, and Zn or an alloy including such a metal.

The lower plated electrode is preferably made of Ni that provides a solder barrier function and the upper plated electrode is preferably made of Sn or Au having excellent solderability.

For example, when first internal electrode layer 16 a and second internal electrode layer 16 b are made of Ni, the lower plated electrode is preferably made of Cu that is well joined to Ni. The upper plated electrode should only be provided as necessary, and each of first external electrode 30 a to fourth external electrode 30 d may include only the lower plated electrode. The upper plated electrode may define and function as an outermost layer of the plated layer, or another plated electrode may further be provided on a surface of the upper plated electrode.

When external electrode 30 includes only the plated layer without underlying electrode layer 32, one plated layer without underlying electrode layer 32 preferably has a thickness not smaller than about 1 μm and not larger than about 15 μm, for example.

The plated layer preferably includes no glass. A ratio of a metal per unit volume of the plated layer is preferably not lower than about 99 volume %, for example.

A dimension in length direction z of multilayer ceramic capacitor 10 including multilayer body 12 and first external electrode 30 a to fourth external electrode 30 d is defined as an L dimension, a dimension in height direction x of multilayer ceramic capacitor 10 including multilayer body 12 and first external electrode 30 a to fourth external electrode 30 d is defined as a T dimension, and a dimension in width direction y of multilayer ceramic capacitor 10 including multilayer body 12 and first external electrode 30 a to fourth external electrode 30 d is defined as a W dimension.

Although the dimension of multilayer ceramic capacitor 10 is not particularly limited, multilayer ceramic capacitor 10 has, for example, the L dimension in length direction z not smaller than about 1.0 mm and not larger than about 3.2 mm, the W dimension in width direction y not smaller than about 0.5 mm and not larger than about 2.5 mm, and the T dimension in height direction x not smaller than about 0.3 mm and not larger than about 2.5 mm. The dimension of multilayer ceramic capacitor 10 can be measured with a microscope.

In multilayer ceramic capacitor 10 shown in FIG. 1 , the number of first internal electrode layers 16 a is larger than the number of second internal electrode layers 16 b and at least two first internal electrode layers 16 a are successively layered. Therefore, multilayer ceramic capacitor 10 achieves improved conduction from first internal electrode layer 16 a and second internal electrode layer 16 b to external electrode 30 while an increase in capacitance thereof is reduced or prevented, and thus it achieves reduction or prevention of an increase in DC resistance.

In multilayer ceramic capacitor 10 shown in FIG. 1 , second internal electrode layer 16 b is larger in thickness than first internal electrode layer 16 a. Therefore, even when the number of second internal electrode layers 16 b is reduced in order to lower the capacitance of multilayer ceramic capacitor 10, connectivity between second internal electrode layers 16 b and third external electrode 30 c and connectivity between second internal electrode layers 16 b and fourth external electrode 30 d can sufficiently be ensured.

2. Method of Manufacturing Multilayer Ceramic Capacitor

A non-limiting example of a method of manufacturing a multilayer ceramic capacitor according to a preferred embodiment of the present invention will now be described.

Initially, a dielectric sheet for a dielectric layer and a conductive paste for an internal electrode are prepared. The dielectric sheet and the conductive paste for the internal electrode layer include a binder and a solvent. A known binder or a known solvent may be used.

The conductive paste for the internal electrode layer is printed in a prescribed pattern on the dielectric sheet, for example, by screen printing or gravure printing. The dielectric sheet having a pattern of the first internal electrode layer formed and the dielectric sheet having a pattern of the second internal electrode layer formed are thus prepared.

More specifically, a screen plate for printing the first internal electrode layer and a screen plate for printing the second internal electrode layer are separately prepared, and the pattern of each internal electrode layer can be printed by, for example, using a printer capable of separate printing using the two types of screen plates. The pattern of the second internal electrode layer is printed to have a larger thickness than the pattern of the first internal electrode layer.

By layering the sheets each with the first internal electrode layer printed and the sheets each with the second internal electrode layer printed to obtain a desired structure, a portion to be inner layer portion 18 is formed. The sheet with the first internal electrode layer printed is larger in number than the sheet having the second internal electrode layer printed, and at least two sheets including the first internal electrode layer printed are successively layered.

Then, a prescribed number of dielectric sheets with no pattern of the internal electrode layer printed are layered to form a portion to be second main-surface-side outer layer portion 20 b on the side of the second main surface. Thereafter, the portion to be inner layer portion 18 formed in the step described above is layered on the portion to be second main-surface-side outer layer portion 20 b, and a prescribed number of dielectric sheets with no pattern of the internal electrode layer printed are layered on the portion to be inner layer portion 18. A portion to be first main-surface-side outer layer portion 20 a on the side of the first main surface is thus formed. A layered sheet is thus formed.

In succession, the layered sheet is pressed in a direction of layering by, for example, isostatic pressing to make a multilayer block.

Then, the multilayer block is cut in a prescribed size to obtain a multilayer chip. A corner and a ridgeline of the multilayer chip may be rounded by barrel polishing.

Then, the cut multilayer chip is fired to make multilayer body 12. A temperature for firing is preferably not lower than about 900° C. and not higher than about 1400° C., although it is dependent on a material for dielectric layer 14 or internal electrode layer 16.

Underlying Electrode Layer

In succession, third underlying electrode layer 32 c of third external electrode 30 c is formed on first side surface 12 c of multilayer body 12 obtained by firing, and fourth underlying electrode layer 32 d of fourth external electrode 30 d is formed on second side surface 12 d of multilayer body 12.

In forming the baked layer as underlying electrode layer 32, a conductive paste including a glass component and a metal component is applied and thereafter baked to form the baked layer as underlying electrode layer 32. A temperature for baking at this time is preferably not lower than about 700° C. and not higher than about 900° C., for example.

Various methods can be used as the method of forming the baked layer. For example, a method of extruding a conductive paste through a slit and applying the conductive paste can be used. In this method, by increasing an amount of the extruded conductive paste, underlying electrode layer 32 can be formed not only on first side surface 12 c and second side surface 12 d but also on a portion of first main surface 12 a and a portion of second main surface 12 b.

A roller transfer method can also be used. In the roller transfer method, in forming underlying electrode layer 32 not only on first side surface 12 c and second side surface 12 d but also on a portion of first main surface 12 a and a portion of second main surface 12 b, by increasing a pressure in pressing in roller transfer, underlying electrode layer 32 can be formed as far as a portion of first main surface 12 a and a portion of second main surface 12 b.

Then, first underlying electrode layer 32 a of first external electrode 30 a is formed on first end surface 12 e of multilayer body 12 obtained by firing and second underlying electrode layer 32 b of second external electrode 30 b is formed on second end surface 12 f of multilayer body 12.

In forming the baked layer as underlying electrode layer 32 as in forming underlying electrode layer 32 of each of third external electrode 30 c and fourth external electrode 30 d, a conductive paste including a glass component and a metal component is applied and thereafter baked to form the baked layer as underlying electrode layer 32. A temperature for baking at this time is preferably not lower than about 700° C. and not higher than about 900° C., for example.

In a method of forming the baked layer as underlying electrode layer 32 of each of first external electrode 30 a and second external electrode 30 b, a method of extruding a conductive paste through a slit and applying the conductive paste or a roller transfer method can be used.

In baking, third underlying electrode layer 32 c of third external electrode 30 c, fourth underlying electrode layer 32 d of fourth external electrode 30 d, first underlying electrode layer 32 a of first external electrode 30 a, and second underlying electrode layer 32 b of second external electrode 30 b may simultaneously be baked, or third underlying electrode layer 32 c of third external electrode 30 c and fourth underlying electrode layer 32 d of fourth external electrode 30 d may be baked separately from first underlying electrode layer 32 a of first external electrode 30 a and second underlying electrode layer 32 b of second external electrode 30 b.

Conductive Resin Layer

When underlying electrode layer 32 is formed from a conductive resin layer, the conductive resin layer can be formed by a method described below. The conductive resin layer may be formed on a surface of the baked layer or the conductive resin layer alone may be directly formed on multilayer body 12 without forming the baked layer.

In the method of forming a conductive resin layer, the conductive resin layer is formed by applying a conductive resin paste including a thermosetting resin and a metal component onto the baked layer or multilayer body 12, subjecting the conductive resin paste to heat treatment at a temperature not lower than about 250° C. and not higher than about 550° C., for example, and thermally curing the resin. An N₂ atmosphere is preferably used as an atmosphere for heat treatment. In order to prevent scattering of the resin and oxidation of various metal components, a concentration of oxygen is preferably reduced to about 100 ppm or lower, for example.

For example, the method of extruding a conductive resin paste through a slit and applying the conductive resin paste or the roller transfer method can be used as the method of applying the conductive resin paste, as in the method of forming underlying electrode layer 32 from the baked layer.

Thin Layer

In forming underlying electrode layer 32 from a thin layer, the underlying electrode layer can be formed at a desired location where external electrode 30 is to be formed by using masking or the like, for example, with a thin film formation method such as sputtering or vapor deposition. The underlying electrode layer formed from the thin layer is a layer not larger than, for example, about 1 μm that results from deposition of metal particles.

Plated Electrode

A plated electrode may be provided in second section 26 b, third section 26 c, fifth section 28 b, and sixth section 28 c where internal electrode layer 16 of multilayer body 12 is exposed, without providing underlying electrode layer 32. In this case, the plated electrode can be formed by a method below.

First end surface 12 e and second end surface 12 f of multilayer body 12 are plated to form lower plated electrodes on second section 26 b and third section 26 c which are the exposed portions of first internal electrode layer 16 a, respectively. Similarly, first side surface 12 c and second side surface 12 d of multilayer body 12 are plated to form lower plated electrodes on fifth section 28 b and sixth section 28 c which are the exposed portions of second internal electrode layer 16 b, respectively. In plating, any of electrolytic plating and electroless plating may be used. Electroless plating, however, is disadvantageous due to a complicated process, because it requires pre-treatment with a catalyst to improve a rate of precipitation of plating. Therefore, electrolytic plating is preferably used. Barrel plating, for example, is preferably used as a plating method. An upper plated electrode formed on a surface of the lower plated electrode may similarly be formed as necessary.

In succession, as necessary, plated layer 34 is formed on the surface of underlying electrode layer 32, the surface of the conductive resin layer or the surface of the lower plated electrode, and the surface of the upper plated electrode.

More specifically, in the present preferred embodiment, a Ni plated layer is formed as the lower plated layer on underlying electrode layer 32 which is the baked layer and an Sn plated layer is formed as the upper plated layer. The Ni plated layer and the Sn plated layer are successively formed, for example, by barrel plating. In plating, any of electrolytic plating and electroless plating may be used. Electroless plating, however, is disadvantageous due to a complicated process, because it requires pre-treatment with a catalyst to improve a rate of precipitation of plating. Therefore, electrolytic plating is preferably used.

Multilayer ceramic capacitor 10 according to the present preferred embodiment is manufactured as described above.

3. Experimental Example

In order to check advantageous effects of the multilayer ceramic capacitor according to a preferred embodiment of the present invention described above, a multilayer ceramic capacitor was manufactured as a sample in an experiment, and a heat generation characteristic test (variation in temperature with variation in current), a test for measuring a DC resistance (Rdc) of the internal electrode layer, and a test for checking connection between the internal electrode layer and the external electrode were conducted.

(1) Specifications of Sample in Example

A multilayer ceramic capacitor according to Example of a preferred embodiment of the present invention with specifications as below was initially made in accordance with the method of manufacturing the multilayer ceramic capacitor described above.

Example

-   -   Structure of multilayer ceramic capacitor: three-terminal (see         FIG. 1 )     -   Dimension L×W×T of multilayer ceramic capacitor (including a         designed value): about 1.6 mm×about 0.8 mm×about 0.6 mm     -   Material for dielectric layer: BaTiO₃     -   Capacitance: see Example 1 to Example 12 in Table 1     -   Rated voltage: see Example 1 to Example 12 in Table 1     -   Structure of LT cross-section: see FIG. 4 (the second internal         electrode layers being arranged to divide the region where at         least two first internal electrode layers were successively         layered (internal electrode layered portion) into a plurality of         regions), FIG. 4 showing Example 6     -   Structure of internal electrode     -   First internal electrode layer

Material: Ni

Shape: see FIG. 6

Number of layers: see Example 1 to Example 12 in Table 1

Thickness: about 1.0 μm

-   -   Second internal electrode layer

Material: Ni

Shape: see FIG. 7 for Example 1 to Example 6 and see FIG. 8 for Example 7 to Example 12

Number of layers: see Example 1 to Example 12 in Table 1

Thickness: about 1.5 μm

-   -   Structure of external electrode     -   First external electrode and second external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 45 μm

Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

-   -   Third external electrode and fourth external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 30 μm

Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

(2) Specifications of Sample in Comparative Example

In succession, multilayer ceramic capacitors according to Comparative Example 1 and Comparative Example 2 with specifications as described below were made.

Comparative Example 1

As compared with the multilayer ceramic capacitor according to Example, the multilayer ceramic capacitor according to Comparative Example is a three-terminal multilayer ceramic capacitor identical to the multilayer ceramic capacitor in Example except for alternate layering of the first internal electrode layers and the second internal electrode layers and difference in number of internal electrode layers.

FIG. 9 is a cross-sectional view showing an exemplary multilayer ceramic capacitor (Comparative Example 1-3) according to Comparative Example 1. A multilayer ceramic capacitor 1A according to Comparative Example 1 includes a multilayer body 2 having a parallelepiped shape, an external electrode 3 on each of opposing end surfaces, and an external electrode 4 on each of opposing side surfaces. Multilayer body 2 includes a plurality of layered dielectric layers 5 and a plurality of first internal electrode layers 6 a and a plurality of second internal electrode layers 6 b layered on dielectric layer 5. First internal electrode layers 6 a and second internal electrode layers 6 b are alternately layered with dielectric layers 5 being interposed.

Details of the specifications will be described below.

-   -   Structure of multilayer ceramic capacitor: three-terminal (see         FIG. 9 )     -   Dimension L×W×T of multilayer ceramic capacitor (including a         designed value): about 1.6 mm×about 0.8 mm×about 0.6 mm     -   Material for dielectric layer: BaTiO₃     -   Capacitance: see Comparative Example 1-1 to Comparative Example         1-12 in Table 2     -   Rated voltage: see Comparative Example 1-1 to Comparative         Example 1-12 in Table 2     -   Structure of LT cross-section: see FIG. 9 (the first internal         electrode layer and the second electrode layer being alternately         layered), FIG. 9 showing Comparative Example 1-3 in Table 2     -   Structure of internal electrode     -   First internal electrode layer

Material: Ni

Shape: see FIG. 6

Number of layers: see Comparative Example 1-1 to Comparative Example 1-12 in Table 2

Thickness: about 1.0 μm

-   -   Second internal electrode layer

Material: Ni

Shape: see FIG. 7 for Comparative Example 1-1 to Comparative Example 1-6 and see FIG. 8 for Comparative Example 1-7 to Comparative Example 1-12

Number of layers: see Comparative Example 1-1 to Comparative Example 1-12 in Table 2

Thickness: about 1.0 μm

-   -   Structure of external electrode     -   First external electrode and second external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 45 μm

Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

-   -   Third external electrode and fourth external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 30 μm

Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

Comparative Example 2

As compared with the multilayer ceramic capacitor according to Example, a multilayer ceramic capacitor according to Comparative Example is a three-terminal multilayer ceramic capacitor identical to the multilayer ceramic capacitor in Example except for a thickness identical between the first internal electrode layer and the second internal electrode layer.

FIG. 10 is a cross-sectional view showing an exemplary multilayer ceramic capacitor (Comparative Example 2-3) according to Comparative Example 2. A multilayer ceramic capacitor 1B according to Comparative Example 2 includes multilayer body 2 having a parallelepiped shape, external electrode 3 on each of opposing end surfaces, and external electrode 4 on each of opposing side surfaces. Multilayer body 2 includes a plurality of layered dielectric layers 5 and a plurality of first internal electrode layers 6 a and a plurality of second internal electrode layers 6 b layered on dielectric layers 5. First internal electrode layers 6 a are larger in number than second internal electrode layers 6 b and at least two first internal electrode layers 6 a are successively layered. In multilayer ceramic capacitor 1B shown in FIG. 10 , second internal electrode layers 6 b are arranged to divide an internal electrode layered portion 7 which is a region where at least two first internal electrodes 6 a are successively layered into a plurality of internal electrode layered portions 7 a, 7 b, 7 c, . . . , and 7 i.

Details of the specifications will be shown below.

-   -   Structure of multilayer ceramic capacitor: three-terminal (see         FIG. 10 )     -   Dimension L×W×T of multilayer ceramic capacitor (including a         designed value): about 1.6 mm×about 0.8 mm×about 0.6 mm     -   Material for dielectric layer: BaTiO₃     -   Capacitance: see Comparative Example 2-1 to Comparative Example         2-12 in Table 3     -   Rated voltage: see Comparative Example 2-1 to Comparative         Example 2-12 in Table 3     -   Structure of LT cross-section: see FIG. 10 (the second internal         electrode layers being arranged to divide the region (internal         electrode layered portion) where at least two first internal         electrode layers were successively layered into a plurality of         regions), FIG. 10 showing Comparative Example 2-3 in Table 3     -   Structure of internal electrode     -   First internal electrode layer

Material: Ni

Shape: see FIG. 6

Number of layers: see Comparative Example 2-1 to Comparative Example 2-12 in Table 3

Thickness: about 1.0 μm

-   -   Second internal electrode layer

Material: Ni

Shape: see FIG. 7 for Comparative Example 2-1 to Comparative Example 2-6 and see FIG. 8 for Comparative Example 2-7 to Comparative Example 2-12

Number of layers: see Comparative Example 2-1 to Comparative Example 2-12 in Table 3

Thickness: about 1.0 μm

-   -   Structure of external electrode     -   First external electrode and second external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 45 μm Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

-   -   Third external electrode and fourth external electrode

Underlying electrode layer: baked layer including conductive metal (Cu) and glass component

Thickness of end surface in central portion: about 30 μm

Plated layer: two-layered structure of Ni plated layer and Sn plated layer

Thickness of Ni plated layer: about 4 μm

Thickness of Sn plated layer: about 4 μm

Tables 1 to 3 show samples of Example, Comparative Example 1, and Comparative Example 2 used in the present experimental example.

TABLE 1 The Number The Number of Layered of Layered First Internal Second Internal Rated Capaci- Electrode Electrode Voltage tance Layers Layers (V) (nF) (Count) (Count) Example 1 16 220 70 25 Example 2 25 100 59 20 Example 3 25 47 83 10 Example 4 50 22 65 8 Example 5 50 15 74 6 Example 6 50 10 79 4 Example 7 50 4.70 57 10 Example 8 50 2.20 80 5 Example 9 50 1.00 86 3 Example 10 50 0.47 65 3 Example 11 50 0.22 70 2 Example 12 50 0.10 70 2

TABLE 2 The Number The Number of Layered of Layered First Internal Second Internal Rated Capaci- Electrode Electrode Voltage tance Layers Layers (V) (nF) (Count) (Count) Comparative 16 220 24 25 Example 1-1 Comparative 25 100 19 20 Example 1-2 Comparative 25 47 9 10 Example 1-3 Comparative 50 22 7 8 Example 1-4 Comparative 50 15 5 6 Example 1-5 Comparative 50 10 3 4 Example 1-6 Comparative 50 4.70 9 10 Example 1-7 Comparative 50 2.20 4 5 Example 1-8 Comparative 50 1.00 2 3 Example 1-9 Comparative 50 0.47 2 3 Example 1-10 Comparative 50 0.22 1 2 Example 1-11 Comparative 50 0.10 1 2 Example 1-12

TABLE 3 The Number of The Number of Rated Capac- Layered First Layered Second Voltage itance Internal Electrode Internal Electrode (V) (nF) Layers (Count) Layers (Count) Comparative 16 220 70 25 Example 2-1 Comparative 25 100 59 20 Example 2-2 Comparative 25 47 83 10 Example 2-3 Comparative 50 22 65 8 Example 2-4 Comparative 50 15 74 6 Example 2-5 Comparative 50 10 79 4 Example 2-6 Comparative 50 4.70 57 10 Example 2-7 Comparative 50 2.20 80 5 Example 2-8 Comparative 50 1.00 86 3 Example 2-9 Comparative 50 0.47 65 3 Example 2-10 Comparative 50 0.22 70 2 Example 2-11 Comparative 50 0.10 70 2 Example 2-12

(3) Heat Generation Characteristic Test (Variation in Temperature with Variation in Current)

In samples according to Example and samples according to Comparative Example 1 and Comparative Example 2, a thermocouple was placed in contact with the surface of the multilayer body of each sample, a DC current was fed between the first external electrode and the second external electrode, and increase in surface temperature of each sample was measured. A magnitude of the current to each sample was between 0 A and 5 A, and variation in temperature of each sample was measured for each magnitude of the current.

The samples in the heat generation characteristic test were as follows. In Example, the sample (having the capacitance of about 10 nF and including seventy-nine layered first internal electrode layers and four layered second internal electrode layers) in Example 6 was used. In Comparative Example 1, the sample (having the capacitance of about 47 nF and including nine layered first internal electrode layers and ten layered second internal electrode layers) in Comparative Example 1-3 was used. In Comparative Example 2, the sample (having the capacitance of about 47 nF and including eighty-three layered first internal electrode layers and ten layered second internal electrode layers) in Comparative Example 2-3 was used. Three samples each were used, and an average value of the samples was calculated. A temperature increase value (ΔT) was calculated by subtraction of a surface temperature of the multilayer body−room temperature.

(4) Test for Measuring DC Resistance (Rdc) of Internal Electrode Layer

In the samples according to Example and the samples according to Comparative Example 1, a potential difference between the first external electrode and the second external electrode was measured while a current of about 100 mA was fed between the first external electrode and the second external electrode, and a value of the potential difference/100 mA was calculated as the DC resistance (Rdc). As shown in Tables 1 and 2, a value of the capacitance was different among the samples in Example and Comparative Example 1. Twenty samples were prepared for each capacitance of the samples in Example and Comparative Example 1 and an average value of the samples was calculated.

(5) Test for Checking Connection Between Internal Electrode Layer and External Electrode

Among the samples according to Example and the samples according to Comparative Example 2, a sample having the DC resistance equal to or higher than a prescribed threshold value was determined as defective in connection, and a ratio of the occurrence of defective connection to the total number of samples in the entire lot was calculated. As shown in Tables 1 and 3, the number of layered second internal electrode layers was different among the samples in Example and Comparative Example 2. In order to set each sample to have a prescribed capacitance, the number of layered first internal electrode layers was also varied. Ten thousand samples according to each of Example and Comparative Example 2 were prepared for each number of layered second internal electrode layers.

Regarding an evaluation result, Table 4 and FIG. 11 show results of the heat generation characteristic test, Tables 5 and and FIG. 12 show results of the test for measuring the DC resistance of the internal electrode layer, and Tables 7 and 8 and FIG. 13 show results of the test for checking connection between the internal electrode layers and the external electrode.

TABLE 4 Temperature Increase

 (° C.) Current Comparative Comparative Example (A) Example 1-3 Example 2-3 6 0 0 0 0 1 3 0.9 0.6 2 9 3.2 2.4 3 19 6.1 5.7 4 32 12.2 11.1 5 50 18.9 17.3

TABLE 5 Capacitance DC Resistance (nF) (mΩ) Example 1 220 4.5 Example 2 100 5.2 Example 3 47 3.5 Example 4 22 4.6 Example 5 15 4.1 Example 6 10 3.7 Example 7 4.70 5.3 Example 8 2.20 4.1 Example 9 1.00 3.3 Example 10 0.47 4.5 Example 11 0.22 4.1 Example 12 0.10 4.1

TABLE 6 Capacitance DC Resistance (nF) (mΩ) Comparative Example 1-1 220 7.6 Comparative Example 1-2 100 9.8 Comparative Example 1-3 47 20.7 Comparative Example 1-4 22 24.8 Comparative Example 1-5 15 34.2 Comparative Example 1-6 10 54.0 Comparative Example 1-7 4.70 65.0 Comparative Example 1-8 2.20 75.0 Comparative Example 1-9 1.00 96.7 Comparative Example 1-10 0.47 122.0 Comparative Example 1-11 0.22 149.4 Comparative Example 1-12 0.10 158.1

TABLE 7 The Number of Layered Ratio of Second Internal Electrode Defective Layers Connection (Count) (%) Example 1 25 0.00 Example 2 20 0.00 Example 3 10 0.00 Example 4 8 0.00 Example 5 6 0.00 Example 6 4 0.00 Example 7 10 0.00 Example 8 5 0.00 Example 9 3 0.00 Example 10 3 0.01 Example 11 2 0.00 Example 12 2 0.02

TABLE 8 The Number of Layered Ratio of Second Internal Electrode Defective Layers Connection (Count) (%) Comparative Example 2-1 25 0.00 Comparative Example 2-2 20 0.00 Comparative Example 2-3 10 0.01 Comparative Example 2-4 8 0.27 Comparative Example 2-5 6 0.11 Comparative Example 2-6 4 0.37 Comparative Example 2-7 10 0.05 Comparative Example 2-8 5 0.17 Comparative Example 2-9 3 1.29 Comparative Example 2-10 3 0.57 Comparative Example 2-11 2 0.63 Comparative Example 2-12 2 0.17

(6) Results of Experiment

(a) Results in Heat Generation Characteristic Test

According to Table 4 and FIG. 11 , it was confirmed that, since the sample of the multilayer ceramic capacitor in each of Example and Comparative Example 2 included the internal electrode layered portion which was the region where at least two first internal electrode layers were successively layered, not only a larger number of first internal electrode layers were provided and a larger number of first internal electrode layers connected in parallel were provided, but also conduction between the internal electrode layers and the external electrode was excellent, and thus the DC resistance was reduced and consequently an amount of heat generation was reduced at any current value and an increase in temperature could be reduced or prevented.

An increase in temperature was slightly less in each sample in Example than in each sample in Comparative Example 2. This may be because, unlike each sample in Comparative Example 2, in each sample in Example, the second internal electrode layer was larger in thickness than the first internal electrode layer, and thus heat in the multilayer ceramic capacitor conducted to the second internal electrode layer and heat was readily radiated from the third external electrode and the fourth external electrode.

On the other hand, the sample of the multilayer ceramic capacitor in Comparative Example 1 was structured such that the first internal electrode layers and the second internal electrode layers were alternately layered. Therefore, in the sample as in Comparative Example 1-3 including a relatively small number of layered internal electrode layers of each type and being low in capacitance, not only the number of first internal electrode layers was small and the number of first internal electrode layers connected in parallel was small, but also conduction between the internal electrode layers and the external electrode was reduced and thus the DC resistance was higher. It was consequently confirmed that the amount of heat generation greatly increased with an increase in current value and the sample in Comparative Example 1 had a larger increase in temperature than the samples in Example and Comparative Example 2.

(b) Results of Test for Measuring DC Resistance of Internal Electrode Layer

It was confirmed according to Table 5 and FIG. 12 that, since the sample of the multilayer ceramic capacitor in Example included the internal electrode layered portion which was the region where at least two first internal electrode layers were successively layered, not only a larger number of first internal electrode layers were provided and a larger number of first internal electrode layers connected in parallel were provided, but also conduction between the internal electrode layers and the external electrode was excellent and thus the value of the DC resistance in Example 1 to Example 12 was about 5.5 mΩ or lower at any capacitance.

On the other hand, it was confirmed according to Table 6 and FIG. 12 that, since the sample of the multilayer ceramic capacitor in Comparative Example 1 was structured such that the first internal electrode layers and the second internal electrode layers were alternately layered and the number of layered first internal electrode layers and the number of layered second internal electrode layers decreased in the order from Comparative Example 1-1 to Comparative Example 1-6 and from Comparative Example 1-7 to Comparative Example 1-12 for lowering the capacitance, the value of the DC resistance greatly increased.

(c) Results of Test for Checking Connection Between Internal Electrode Layer and External Electrode

It was confirmed according to Table 7 and FIG. 13 that, since the second internal electrode layer connected to the third external electrode and the fourth external electrode was larger in thickness than the first internal electrode layer in the sample of the multilayer ceramic capacitor in Example, defective connection did not occur in Examples 1 to 9 and 11 and substantially no defective connection occurred as exemplified as a ratio of defective connection being about 0.01% in Example 10 where three second internal electrode layers were layered and a ratio of defective connection being about 0.02% in Example 12 where two second internal electrode layers were layered.

On the other hand, it was confirmed according to Table and FIG. 13 that, in the sample of the multilayer ceramic capacitor in Comparative Example 2, the thickness of the second internal electrode layer connected to the third external electrode and the fourth external electrode was the same or substantially the same as the thickness of the first internal electrode layer which was relatively small, and in particular in Comparative Examples 2-4 to 2-6 and Comparative Examples 2-8 to 2-12, the number of layered second internal electrode layers was eight or smaller, and therefore the ratio of defective connection was about 0.1% or higher and defective connection between the second internal electrode layer and the external electrode was likely.

As set forth above, it was confirmed that, in the sample of the multilayer ceramic capacitor according to Example, the first internal electrode layers were larger in number than the second internal electrode layers and at least two first internal electrode layers were successively layered, and thus not only a larger number of first internal electrode layers were provided and a larger number of first internal electrode layers connected in parallel were provided while an increase in capacitance of the multilayer ceramic capacitor was reduced, but also conduction between the internal electrode layers and the external electrode was improved and an increase in DC resistance was reduced or prevented.

It was confirmed that, in a multilayer ceramic capacitor according to a preferred embodiment of the present invention, the second internal electrode layer was larger in thickness than the first internal electrode layer, and thus even when the number of the second internal electrode layers was reduced to reduce the capacitance of the multilayer ceramic capacitor, connectivity between the second internal electrode layer and the third external electrode and connectivity between the second internal electrode layer and the fourth external electrode could be sufficiently ensured.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A multilayer ceramic capacitor comprising: a multilayer body including a plurality of layered dielectric layers, a first main surface and a second main surface opposed to each other in a height direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the height direction, and a first side surface and a second side surface opposed to each other in a width direction orthogonal or substantially orthogonal to the height direction and the length direction; a plurality of first internal electrode layers on the plurality of dielectric layers and extending to the first end surface and the second end surface; a plurality of second internal electrode layers on the plurality of dielectric layers and extending to the first side surface and the second side surface; a first external electrode on the first end surface and connected to the plurality of first internal electrode layers; a second external electrode on the second end surface and connected to the plurality of first internal electrode layers; a third external electrode on the first side surface and connected to the plurality of second internal electrode layers; and a fourth external electrode on the second side surface and connected to the plurality of second internal electrode layers; wherein a number of the plurality of first internal electrode layers is larger than a number of the plurality of second internal electrode layers, at least two of the plurality of first internal electrode layers are successively layered, and a thickness of each of the plurality of second internal electrode layers is larger than a thickness of each of the plurality of first internal electrode layers.
 2. The multilayer ceramic capacitor according to claim 1, wherein the plurality of second internal electrode layers divide a region where at least two of the plurality of first internal electrode layers are successively layered into a plurality of regions.
 3. The multilayer ceramic capacitor according to claim 2, wherein a single second internal electrode layer of the plurality of second internal electrode layers divides the region where at least two of the plurality of first internal electrode layers are successively layered into the plurality of regions.
 4. The multilayer ceramic capacitor according to claim 2, wherein at least two of the plurality of second internal electrode layers are successively layered to divide the region where at least two of the plurality of first internal electrode layers are successively layered into the plurality of regions.
 5. The multilayer ceramic capacitor according to claim 1, wherein a second internal electrode layer of the plurality of second internal electrode layers is provided between a region where at least two of the plurality of first internal electrode layers located on a side of the first main surface are successively layered and the first main surface and between a region where at least two of the plurality of first internal electrode layers located on a side of the second main surface are successively layered and the second main surface.
 6. The multilayer ceramic capacitor according to claim 1, wherein a second internal electrode layer of the plurality of second internal electrode layers is not provided between a region where at least two of the plurality of first internal electrode layers located on a side of the first main surface are successively layered and the first main surface and between a region where at least two of the plurality of first internal electrode layers located on a side of the second main surface are successively layered and the second main surface.
 7. The multilayer ceramic capacitor according to claim 1, wherein a dielectric layer adjacent to the second internal electrode layer has a larger thickness than a dielectric layer between the plurality of first internal electrode layers.
 8. The multilayer ceramic capacitor according to claim 1, wherein each of the plurality of second internal electrode layers includes a portion located in a central portion of a respective one of the plurality of dielectric layers and a portion extending from the portion located in the central portion of the respective one of the plurality of dielectric layers to the first side surface and the second side surface; and a relationship of A≥B is satisfied, where A represents a width of the portion located in the central portion of the respective one of the plurality of dielectric layers in the length direction that connects between the first end surface and the second end surface and B represents a width of the portion extending in the length direction that connects between the first end surface and the second end surface.
 9. The multilayer ceramic capacitor according to claim 1, wherein the multilayer body includes an inner layer portion, a first main-surface-side outer layer portion, and a second main-surface-side outer layer portion; the inner layer portion includes a plurality of the plurality of dielectric layers, and the plurality of first and second internal electrode layers; the first main-surface-side outer layer portion is located on a side of the first main surface and includes a plurality of the plurality of dielectric layers; and the second main-surface-side outer layer portion is located on a side of the second main surface and includes a plurality of the plurality of dielectric layers.
 10. The multilayer ceramic capacitor according to claim 1, wherein the plurality of dielectric layers include at least one of BaTiO₃, CaTiO₃, SrTiO₃, or CaZrO₃ as a main component.
 11. The multilayer ceramic capacitor according to claim 10, wherein the plurality of dielectric layers include at least one of an Mn compound, an Fe compound, a Cr compound, a Co compound, or an Ni compound as a sub-component.
 12. The multilayer ceramic capacitor according to claim 1, wherein each of the plurality of dielectric layers has a thickness of not smaller than about 0.5 μm and not larger than about 10 μm.
 13. The multilayer ceramic capacitor according to claim 1, wherein a number of the plurality of dielectric layers is not smaller than fifteen and not larger than
 300. 14. The multilayer ceramic capacitor according to claim 1, wherein a number of the plurality of first internal electrode layers is not smaller than 30 and not larger than
 100. 15. The multilayer ceramic capacitor according to claim 1, wherein a number of the plurality of second internal electrode layers is not smaller than one and not larger than
 50. 16. The multilayer ceramic capacitor according to claim 1, wherein a thickness of each of the plurality of first internal electrode layers is not smaller than about 0.5 μm and not larger than about 2.0 μm.
 17. The multilayer ceramic capacitor according to claim 1, wherein a thickness of each of the plurality of second internal electrode layers is not smaller than about 1.0 μm and not larger than about 3.0 μm.
 18. The multilayer ceramic capacitor according to claim 1, wherein a thickness of each of the plurality of second internal electrode layers is at least about 1.2 times a thickness of each of the plurality of first internal electrode layers. 